SUFILTER - applies a zero-phase, sine-squared tapered filter		

 sufilter <stdin >stdout [optional parameters]         		

 Required parameters:                                         		
       if dt is not set in header, then dt is mandatory        	

 Optional parameters:							
       f=f1,f2,...             array of filter frequencies(HZ) 	
       amps=a1,a2,...          array of filter amplitudes		
       dt = (from header)      time sampling interval (sec)        	

 Defaults:f=.10*(nyquist),.15*(nyquist),.45*(nyquist),.50*(nyquist)	
                        (nyquist calculated internally)		
          amps=0.,1.,...,1.,0.  trapezoid-like bandpass filter		

 Examples of filters:							
 Bandpass:   sufilter <data f=10,20,40,50 | ...			
 Bandreject: sufilter <data f=10,20,30,40 amps=1.,0.,0.,1. | ..	
 Lowpass:    sufilter <data f=10,20,40,50 amps=1.,1.,0.,0. | ...	
 Highpass:   sufilter <data f=10,20,40,50 amps=0.,0.,1.,1. | ...	
 Notch:      sufilter <data f=10,12.5,35,50,60 amps=1.,.5,0.,.5,1. |..	

 Credits:
      CWP: John Stockwell, Jack Cohen

 Possible optimization: Do assignments instead of crmuls where
 filter is 0.0.

 Trace header fields accessed: ns, dt